Battery bank cables, what size to use?

[scanzel]

What size of battery interconnect cable are you using? I have 8/ 100 amp hour AGM batteries that will probably be in series/parallel for 24 volts to a 24 volt Magnum 4024 inverter.

[H3Jim]

Bigger is generally better.  For DC power, length is almost as important as gauge.

I used as short a lengths as I could plan for, and went 4 ought.  Thats about as big as is easily available and is also flexible enough to use.

Why use your precious and expensive power just to heat up wires? supersize it.

[bowmaga]

I'm getting ready to set up the same type system and power my 2500 watt xantrex inverter.  The inverter book told me not to use anything less than 4/0 wire to power anything from 0-10' and didn;t recommend having the inverter more than 10' away from battery bank.  I'm using flag style battery terminals to reduce the work of connecting the wire to the battery terminals.  I can solder or crimp the terminals to the 4/0 wire.  The 4/0 wire is going to run you anywhere from $7-$9 per foot.  I got 10' of red and 10' of black and plan on wiring all 8 of my batteries together and then hanging my inverter right at the end of the battery run.  The you'll need a little 4/0 for the ground wire.  It really depends on the wattage of your inverter....but as H3Jim said, bigger is better.  Good welding fine strand wire is the best.  Flexible and you that will lower the amount of amps lost in the run of wire.  Terminals cost me about $5 a piece.  Here is where i got my stuff.  Don;t know if it was the cheapest, but they were easy to talk to and i could get everything in one place.  http://shop.genuinedealz.com/

[H3Jim]

Because I bought my generator, inverter and my batteries from Wrico, he sold me wire and connctors at his cost  if I went to his shop and did the  work.  While several years ago now, and copper has jumped in price, I paid $3 a foot plus about $1.50 each for the crimp connectors.  He has a crimper that I used to make the cables. 

[boogiethecat]

...and don't forget when you wire your banks up, to come in from opposite sides of the bank with your plus and minus wires.  This keeps the batteries completely balanced during heavy loads no matter what the size/resistance of your wires....

[Slow Rider]

I am brand spanking new to this, but, I remember reading somewhere that you didn't want your inverter in the same space as your battery bank.  The idea was the vent gases from the battery could harm the inverter. 

Some of the smart guys will jump in now and tell us what the real deal is.

Frank

[rv_safetyman]

Some random thoughts on this subject.

As noted above, you must think about mounting the inverter in the same compartment as the batteries.  They need to be mounted very close together.  In my case, I built a tight battery box with vents in the bottom (out the floor) and mounted them in the same compartment.

I think you will find that the inverter manual will ask you to mount the two cables together (parallel) for as long a distance as possible to cut down on electrical "noise"

Be sure to put a fuse in the system along with a battery disconnect.  I can give you a fairly good vendor for the fuse later (rushing and can't find it right now).  For the battery shut off switch look at this thread:
http://www.busconversions.com/bbs/index.php?topic=6174.msg62054#msg62054

Jim

[kyle4501]

The gas that escapes batteries is very corrosive. Corrosive gasses & expensive electronics (let's say an inverter) don't play well together. 

If it were me, I'd have a bulkhead between the properly vented battery compartment & the inverter. 
When planing the venting for the battery compartment, I'd be sure to give consideration to where the corrosive gasses are directed. I wouldn't want them getting sucked in with the cooling air for the inverter.

[Blacksheep]

My 6 golf cart batteries are in one bay next to the bulkhead seperating another bay which has my inverter. I mouinted my inverter up higher than the batteries as they are directly on the bay floor but will soon put them in a vented box as well. My inverter directions said to keep them seperate for obvious reasons stated!
BS

[HB of CJ]

Yeah, same answers based upon hard experience.  The closer your $expensive$ invertor is to your also $expensive$ battery bank, the better both will like it.....if the connecting cables are of the proper size.  Using the properly sized cables doesn't add that much $$$.

If you feel the need to have the invertor separate from the batts, then it is super more important that the connective cables are sized to MIMIMUMIZE (sp?) the voltage drop.  Double up the 0000 cables if you have to.  Yes again, wire the batts to equalize the current paths.

Some (most?) instructions may be happy if you run cables based upon about a 2% voltage loss at an average load.  No.  What you should try to do is to run cable that will only see about a 1% voltage loss at maximum load.  See the difference?  Costs you a little more.

Crimping is also important.  We learned that the best low voltage, high amperage connections are crimped WITHOUT using sodder.  We had access to the special, big, heavy, ($expensive$ again) hand crimper which looked kinda like the mother of all bolt cutters.

Dont feel shy about using recycled heavy welding cable.  We found a super deal on 0000 and 000000 cable that was in an actual gold mine and was decommissioned simply because it had reached a certain age.  Multi strand copper inside a very flexible rubber jacket.

Pay the extra money to use the proper cable size, along with having the connections crimped properly using the proper equipment.  This is not a place to try to save $$$$, it may come back to bite you in the end.  Shrink wrapping the connections. Good luck. 

[rv_safetyman]

Concerning the crimping.  I use Del City as a supplier for a lot of my bus and business parts.  Their copper terminals are reasonable:
http://www.delcity.net/delcity/servlet/catalog?parentid=1015&page=1

The hammer type criming tool is ideal for making good connections and is cheap:
http://www.delcity.net/delcity/servlet/catalog?parentid=1027&page=1

Jim

[H3Jim]

Good comment aobuthte battery outgassing.  I used AGM's so thats not an issue.  Althogh they can still outgas, they are much less likely.  and I mounted the inverter high up in the compartment, and the batteries covered, are at the bottom and vented down.

[DrivingMissLazy]

Good comment aobuthte battery outgassing.  I used AGM's so thats not an issue.  Althogh they can still outgas, they are much less likely.  and I mounted the inverter high up in the compartment, and the batteries covered, are at the bottom and vented down.

Curious. Is the gas heavier than air and if the box is vented out the bottom, where does the fresh air come into the box to let the gas out?

Richard.

[H3Jim]

Good question.  If its just hydrogen, that's lighter than air and would rise.  I have no answer, but I have not had any issues, although that's not a guarantee I'm not doing damage that will surface later.

[Nick Badame Refrig/ACC]

Hi Scanzel,

Here is a DC wire calculator.

http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html

Nick-